Generally described, computing devices and communication networks can be utilized to exchange information. In a common application, a computing device can request content from another computing device via the communication network. For example, a user at a computing device, such as a personal computer, can utilize a software browser application, typically referred to as a browser, to request a Web page from a server computing device via the Internet. In such embodiments, the requesting computing device can be referred to as a client computing device and the server computing device can be referred to as a content provider. Generally, the user may request, obtain, and interact with a number of requested Web pages or other content simultaneously, or in sequence, through the software browser application. The collection of content accessed by a client computing device via the software browser application over a period of time may be referred to as a browse session.
Content accessed by a browsing software application, such as Web pages, typically include a number of parts, which can include text, images, videos, etc. Often the collection of parts are integrated to provide a specific look and feel to the Web page. Because content providers typically incur significant expenses in the presentation of content, content providers often include advertising messages as part the content provided to the client computing device. Such advertising messages may either be for the benefit of an advertiser other than the content provider, or may promote products or services sold by the content provider. For example, a shopping Web site may include on its Web pages for advertisements products or services sold by the shopping Web site to promote additional sales. In another example, a content provider may utilize an third party service that provides the content provider financial compensation based on the number of advertisements displayed to users or in the event that a displayed advertisement results in desired interaction with users (e.g., a purchase of an advertised product).
It is common for a content provider to reserve a number of areas, or “slots,” in a Web page for displaying advertising message when the content is displayed at the client computing device. Additionally, a content provider or third-party advertising provider may select from a number of eligible advertising messages to include in the display of the content. In many cases, third parties who wish to advertise through a content provider may purchase placements for their advertising messages in one or more slots of content provided by the content provider. The purchase of an advertising message is often based on a bidding paradigm in which the advertisement associated with a highest bidder is selected.